Hey folks, what the title says pretty much. Im lookin at doing some work to my truck, a '99 silverado. Its got an iron block 5.3 in it. Right now, I just wanna slap a turbo on, nothing too rowdy, mostly for economy but also a little extra power. Eventually I wanna cam it out, change the guts, and make it fast, but that'll wait until I have another vehicle. To the point, how much boost can I run before I have to switch to a higher octane?

 

0psi.

Running high octane is not an option when it comes to boost. 87 octane and boost is just asking for knock/ping.

 

Do us all a favor and sell your truck.

 

While I'm still preparing to turbo my truck, my cam only LQ4 had audible detonation from ~3800 rpm up on 87 octane. Catch can helped a lot, but the timing is still dialed back on 87 octane to not hear detonation. I've used 93 and have recently converted to flex fuel to try E85, the truck doesn't detonate on either. So I agree with FFDP that 0 psi on 87 octane is about right.

 

Before we re-tuned it under load, my Tahoe was pinging on 91 (best I got around here) when it was loaded with the racecar and the P1 was making ~2lbs

Under no circumstance will I ever suggest or run less than 91 on anything except the carb'd 22r in my crawler. Every engine benefits from the timing benefit and trucks especially benefit from the increased knock resistance when we throw cams, intakes, heads and boost at them, then load them down to the bump stops and haul *** to the lake

Run 91 minimum or dont try anything

 

I don't understand where the economy comes in. Do people think that a Ford V6 Ecoboost gets better gas mileage than a V8 because it's turbocharged?

 

While I'm not recommending to run 87, I understand it. At one point, I wanted to try it myself with meth injection. Right now in MD, 93 is $0.90 more a gallon than 87, that is a big difference on vehicles that use a lot of fuel. Thankfully E85 is $0.25 cheaper than 87.

 

Turbo's get better econ on the highway because they increase VE and make the engine work less for the same hp, so lower throttle position for the same speed: less fuel used

 

You can afford a turbo kit and turbo but not the fuel that it requires? I smell a troll...

 

I recall back when Ford released the Ecoboost, magazine tests for mpg showed no average fuel economy improvement between them and their V8 counterparts. I think it was even 1mpg worse in one case. Boost requires more power enrichment.